Measuring device electronics for a measuring device as well as measuring device formed therewith

ABSTRACT

A measuring device electronics comprises a processor and two clock signal generators. One clock signal generator serves for producing a working clock signal, and also for producing a reference clock signal which is dependant on the working clock signal. The other clock signal generator, serves for producing a second reference clock signal, which is independent of the working clock signal. Based on the two independent reference clock signals, a frequency difference, can, to the extent that such is present, be ascertained during operation of the measuring device electronics or of the measuring device formed therewith. The frequency difference, represents a difference between the instantaneous clocking frequency of the first reference clock signal and the instantaneous clocking frequency of the second reference clock signal, and, in this respect, represents a measure for a deviation of an instantaneous clocking frequency, from the nominally predetermined clocking frequency, of the working clock signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a nonprovisional which claims the benefit of U.S.Provisional Application No. 61/491,420, filed on May 31, 2011.

TECHNICAL FIELD

The invention relates to a measuring device electronics for a measuringdevice (especially a measuring device embodied as a measuring and/orswitching device of industrial measurements and automation technologyand/or an electronic measuring device) as well as to such a measuringdevice. Moreover, the invention relates to a method for verifying such ameasuring device.

BACKGROUND DISCUSSIONS

In industrial process measurements technology, especially also inconnection with the automation of chemical processes or procedures forproducing a product from a raw or starting material by the use ofchemical, physical or biological processes and/or the automated controlof industrial plants, electrical measuring devices installed near to theprocess, so called field devices, are applied, such as, for example,Coriolis mass flow measuring devices, density measuring devices,magneto-inductive flow measuring devices, vortex flow measuring devices,ultrasonic flow measuring devices, thermal, mass flow measuring devices,pressure measuring devices, fill level measuring devices, etc., whichserve for producing measured values representing process variables, aswell as measured value signals—in given cases also digital measuredvalue signals—ultimately representing these measured values. The processvariables in each case to be registered can be, depending onapplication, for example, mass flow, density, viscosity, fill level,limit level or the like, of a liquid, a powdered medium, a vaporousmedium or a gaseous medium, which is conveyed or held in a correspondingcontainer, e.g. a pipeline or a tank.

For registering the respective process variables, measuring devices ofthe aforementioned type contain, in each case, a corresponding physicalto electrical, or chemical to electrical, measuring transducer. Such ismost often inserted in a wall of the respective container containing themedium or into the course of a respective line—for example apipeline—conveying the medium, and serves to produce at least onecorresponding electrical measurement signal corresponding to the processvariable to be registered. For processing the measurement signal, themeasuring transducer is further connected with a measuring deviceinternal, operating and evaluating circuit, which is provided in ameasuring device electronics of the measuring device, and which servesfor further processing or evaluation of the at least one measurementsignal, as well as also for generating corresponding measured valuesignals. The latter, in the case of modern measuring devices of the typebeing discussed, is most often formed by means of a processor, such as,for instance, a microprocessor and/or a digital signal processor (DSP),clocked by a corresponding clock signal. Examples of such measuringdevices or measuring transducers, and especially also details concerningtheir application and operation, are described in, among others, DE 10041 166, DE-A 10 2005 032808, the DE-A 37 11 754n, DE-A 39 34 007, DE-A44 12 388, EP-A 1 058 093, EP-A 1 147 463, EP-A 1 158 289, EP-A 1 197732, EP-A 1 669 726, EP-A 525 920, EP-A 591 926, EP-A 866 318, EP-A 926473, EP-A 984 248, US-A 2004/0117675, US-A 2005/0139015, US-A2006/0096390, US-A 2006/0112774, US-A 2006/0120054, US-A 2006/0161359,US-A 2006/0179956, US-A 2007/0217091, US-A 2009/0000392, US-A2009/0038406, US-A 2009/0277281, US-A 2010/0095784, US-A 2010/0236338,US-A 2010/0242623, US-A 2010/0242624, US-A 2010/0255796, U.S. Pat. No.3,878,725, U.S. Pat. No. 4,308,754, U.S. Pat. No. 4,317,116, U.S. Pat.No. 4,468,971, U.S. Pat. No. 4,524,610, U.S. Pat. No. 4,574,328, U.S.Pat. No. 4,594,584, U.S. Pat. No. 4,617,607, U.S. Pat. No. 4,656,353,U.S. Pat. No. 4,716,770, U.S. Pat. No. 4,768,384, U.S. Pat. No.4,777,833, U.S. Pat. No. 4,801,897, U.S. Pat. No. 4,850,213, U.S. Pat.No. 4,879,911, U.S. Pat. No. 4,926,340, U.S. Pat. No. 5,009,109, U.S.Pat. No. 5,024,104, U.S. Pat. No. 5,050,439, U.S. Pat. No. 5,052,230,U.S. Pat. No. 5,065,152, U.S. Pat. No. 5,068,592, U.S. Pat. No.5,131,279, U.S. Pat. No. 5,207,101, U.S. Pat. No. 5,231,884, U.S. Pat.No. 5,359,881, U.S. Pat. No. 5,363,341, U.S. Pat. No. 5,416,723, U.S.Pat. No. 5,469,748, U.S. Pat. No. 5,535,243, U.S. Pat. No. 5,602,345,U.S. Pat. No. 5,604,685, U.S. Pat. No. 5,672,975, U.S. Pat. No.5,687,100, U.S. Pat. No. 5,706,007, U.S. Pat. No. 5,731,527, U.S. Pat.No. 5,742,225, U.S. Pat. No. 5,742,225, U.S. Pat. No. 5,796,011, U.S.Pat. No. 5,804,741, U.S. Pat. No. 5,869,770, U.S. Pat. No. 5,959,372,U.S. Pat. No. 6,006,609, U.S. Pat. No. 6,014,100, U.S. Pat. No.6,051,783, U.S. Pat. No. 6,073,495, U.S. Pat. No. 6,140,940, U.S. Pat.No. 6,236,322, U.S. Pat. No. 6,269,701, U.S. Pat. No. 6,285,094, U.S.Pat. No. 6,311,136, U.S. Pat. No. 6,352,000, U.S. Pat. No. 6,366,436,U.S. Pat. No. 6,397,683, U.S. Pat. No. 6,476,522, U.S. Pat. No.6,480,131, U.S. Pat. No. 6,487,507, U.S. Pat. No. 6,512,358, U.S. Pat.No. 6,513,393, U.S. Pat. No. 6,535,161, U.S. Pat. No. 6,539,819, U.S.Pat. No. 6,556,447, U.S. Pat. No. 6,574,515, U.S. Pat. No. 6,577,989,U.S. Pat. No. 6,640,308, U.S. Pat. No. 6,662,120, U.S. Pat. No.6,666,098, U.S. Pat. No. 6,769,301, U.S. Pat. No. 6,776,053, U.S. Pat.No. 6,799,476, U.S. Pat. No. 6,840,109, U.S. Pat. No. 6,854,055, U.S.Pat. No. 6,920,798, U.S. Pat. No. 7,017,424, U.S. Pat. No. 7,032,045,U.S. Pat. No. 7,073,396, U.S. Pat. No. 7,075,313, U.S. Pat. No.7,133,727, U.S. Pat. No. 7,134,348, U.S. Pat. No. 7,200,503, U.S. Pat.No. 7,360,451, WO-A 00/14 485, WO-A 00/36 379, WO-A 00/48157, WO-A01/02816, WO-A 02/086426, WO-A 02/103327, WO-A 02/45045, WO-A 03/048874,WO-A 2006/073388, WO-A 2008/003627, WO-A 2011/011255, WO-A 88/02 476,WO-A 88/02 853, or WO-A 95/16 897.

In the case of a large number of measuring devices of the type beingdiscussed, for producing the measurement signal, the measuringtransducer is driven during operation by a driver signal generated, atleast at times, by the operating and evaluating circuit in such a mannerthat it acts, at least indirectly, or via a probe directly contactingthe medium, practically directly, on the medium in a manner suitable forthe measuring, on the medium, in order to bring about correspondingreactions there corresponding with the measured variable to beregistered. The driver signal can, in such case, be correspondinglycontrolled as regards, for example, an electrical current level, avoltage level and/or a frequency. To be cited as examples for suchactive measuring transducers, that is measuring transducerscorrespondingly converting an electrical driver signal in the medium,are especially flow measuring transducers serving for measuring media atleast at times flowing, e.g. measuring transducers with at least onecoil operated by the driver signal and producing a magnetic field, or atleast one ultrasonic transmitter driven by the driver signal, or alsofill level and/or limit level transducers serving for measuring and/ormonitoring fill levels in a container, such as, for example, measuringtransducers with freely radiating microwave antennas, with Goubau linesor with vibrating immersion elements.

Devices of the type being discussed have, furthermore, at least onehousing with at least one, usually pressure-tightly and/or explosionresistantly closed chamber accommodating electrical, electronic and/orelectro-mechanical components and/or assemblies of the device, forexample, components of the mentioned operating and evaluating circuit.Thus, for accommodating the measuring device electronics, measuringdevices of the described type most often comprise a comparativelyrobust, especially impact-resistant, pressure-resistant, and/orweather-resistant electronics housing. This can be arranged—as, forexample, provided in U.S. Pat. No. 6,397,683 or WO-A 00/36379—removedfrom the measuring device and connected with this only via a flexibleline; it can, however—as is shown, for example, in EP-A 903 651 or EP-A1 008 836—also be arranged directly on the measuring transducer or on atransducer measuring transducer housing separately housing the measuringtransducer. In given cases, the electronics housing can then, as is, forexample, shown in EP-A 984 248, U.S. Pat. No. 4,594,584, U.S. Pat. No.4,716,770 or U.S. Pat. No. 6,352,000, also serve to accommodate somemechanical components of the measuring transducer, such as, for example,membrane, rod, sleeve or tubular deformation or vibrating elementsoperationally deforming under mechanical action; compare for this alsothe previously mentioned U.S. Pat. No. 6,352,000 or U.S. Pat. No.6,051,783.

In the case of measuring devices, the respective measuring deviceelectronics is usually electrically connected via correspondingelectrical lines to a superordinated electronic data processing systemarranged most often spatially removed from the respective device andmost often also spatially distributed, wherein measured values producedby the respective measuring device are promptly forwarded to this dataprocessing system by means of a measured value signal correspondinglycarrying these measured values. Electrical devices of the described typeare additionally usually connected by means of a data transmissionnetwork provided within the superordinated data processing system withone another and/or with corresponding electronic process controllers,for example, programmable logic controllers, installed on-site orprocess control computers installed in a remote control room, to whichthe measured values produced by means of the measuring device anddigitized and correspondingly suitably encoded are forwarded. By meansof such process control computers, the transmitted measured values canbe further processed and visualized as corresponding measurementresults, e.g. on monitors, and/or be converted into control signals forother field devices embodied as actuating devices, e.g. magnetic valves,electric motors etc. Since modern measuring arrangements most often canalso be directly monitored and, in given cases, controlled and/or can beconfigured by such control computers, associated operating data are in acorresponding manner likewise sent to the measuring device via theaforementioned transmission networks, which are most often datatransmission networks that are hybrid as regards the transmissionphysics and/or the transmission logic. Accordingly, the data processingsystem usually also serves to condition—for example, to suitablydigitize—the measured value signal delivered by the measuring devicecorresponding to the requirements of downstream data transmissionnetworks, and, in given cases, to convert the signal into acorresponding telegram, and/or to evaluate it on-site. For such purpose,in such data processing systems, evaluating circuits electricallycoupled with the respective connecting lines are provided, whichpre-process and/or further process as well as, if required, suitablyconvert the measured values received from the respective measuringand/or switching device. Serving at least sectionally for datatransmission in such industrial data processing systems are fieldbusses,especially serial fieldbusses, such as, for example, FOUNDATIONFIELDBUS, RACKBUS-RS 485, PROFIBUS, etc., or, for example, also networksbased on the ETHERNET standard, as well as the corresponding, most oftencomprehensively standardized, transmission protocols.

Besides the evaluating circuits required for processing and convertingthe measured values delivered by the respectively connected measuringdevices, such superordinated data processing systems most often alsohave electrical supply circuits serving for supplying the connectedmeasuring and/or switching devices with electrical energy. Thus, suchelectrical supply circuits provide corresponding supply voltages (ingiven cases fed directly by the connected fieldbus) for the respectivemeasuring device electronics, and drive the electrical currents flowingthrough the electrical lines connected thereto as well as through therespective measuring device electronics. In such case, a supply circuitcan be associated, for example, in each case, with exactly one measuringdevice, and, together with the evaluating circuit associated with therespective measuring device—for example, united to form a correspondingfieldbus adapter—be accommodated in a shared electronics housing,embodied, for example, as a hatrail module. It is, however, also quiteusual to accommodate supply circuits and evaluating circuits in eachcase in separate electronics housings, in given cases spatially remotefrom one another, and correspondingly to wire these with one another viaexternal lines.

As mentioned, among others, in the previously mentioned EP-A 1 197 732or US-A 2009/0000392, measuring devices of the type being discussed, areat times to be tested—be it at the instigation of the user operating themeasuring device and/or due to a requirement of one of the authoritiesoverseeing the measuring point formed by means of the measuringdevice—as to whether the required accuracy of measurement or that statedin the specification is still reliably achieved, or whether themeasuring device—for instance, as a result of wear of the measuringtransducer and/or aging of the measuring device electronics—no longermeasures sufficiently precisely or no longer in a sufficientlyreproducible manner.

Such tests of the measuring device electronics in the context of asubsequent verification of its measuring functionality, or an equallysubsequent validation of the measured values produced by means of themeasuring device regularly occurs in the case of conventional measuringdevices by a correspondingly certified external testing device beingconnected to the measuring device electronics via a service interface,wherein the external testing device serves to apply at least one definedtest signal corresponding to the at least one measurement signal at theinput of the measuring device electronics for the respective measurementsignal of the measuring transducer. By means of the test signal, aparticular behavior of the measuring transducer, and consequently acorresponding particular measured value for the measured variableotherwise to be registered can thus in each case be simulated. Inassociation therewith, by means of the measuring device electronics, thetest measured values corresponding with the respective test signal canthus be produced and compared with specifications for test measuredvalues corresponding with the respective test signal. If the testmeasured values deviate by less than an allowable highest tolerance fromthe specifications, the measuring device electronics and consequentlythe measuring device has then passed these tests, and consequently, themeasuring device electronics is correspondingly verified and permittedfor further operation.

A disadvantage of such a method for testing measuring device electronicsis particularly to be seen in the fact that, for its performance, normalmeasuring operation of the measuring device must be interrupted, andconsequently the portion of the plant monitored from the measuring pointmust be taken out of operation for the duration of the test. Moreover,such testing requires a special, most often very expensive, testingdevice, which recurringly must undergo very complex recalibration.Furthermore, this kind of testing is regularly performed only bycorrespondingly trained and permitted examiners.

SUMMARY OF THE INVENTION

Taking the above into consideration, an object of the invention is toimprove methods for testing measuring devices of the type beingdiscussed, especially such generating measured values for chemical orphysical measured variables based on a time (e.g. travel time) and/orfrequency or phase angle measurement, respectively, to improve measuringdevice electronics of such measuring devices, with the goal that saidtesting of the measuring device electronics, particularly also in thecontext of a verification of the measuring functionality of therespective measuring device electronics and/or a validation of measuredvalues produced therewith, can occur at least partially with “on-board”means of the measuring device, and, indeed, to the greatest extentpossible also without interruption of the normal measurement operation.

For achieving the object, the invention resides in a measuring deviceelectronics for a measuring device, wherein the measuring deviceelectronics comprises: a processor, for example, one embodied as amicroprocessor or as a digital signal processor; a first clock signalgenerator—for example, one formed by means of a quartz oscillator and/orby means of a PLL circuit and/or by means of an FLL circuit—forproducing a working clock signal clocking the processor with a nominallyconstant clocking frequency and for producing a first reference clocksignal dependant on the working clock signal and having a nominallyconstant clocking frequency, which is smaller than the clockingfrequency of the working clock signal by a predetermined factor; as wellas a second clock signal generator—for example, one formed by means of aquartz oscillator and/or formed by means of a PLL circuit and/or formedby means of an FLL circuit—for producing a second reference clock signalindependent of the working clock signal and serving, for example, as areference for the working clock signal and having a nominally constantclocking frequency, which is smaller than the clocking frequency of theworking clock signal by a predetermined factor.

Furthermore, the invention resides in a measuring device for measuringat least one physical and/or chemical measured variable of a mediumconveyed in a line—, for example, a pipeline or a flume—or in acontainer—for example, a tank or a vat—wherein this measuring devicecomprises such a measuring device electronics as well as a measuringtransducer electrically coupled with said measuring device electronics,wherein this measuring transducer serves for transducing the at leastone measured variable into at least one measurement signal dependentthereon. Moreover, the invention also resides in a method for testingsuch a measuring device—for example, for verifying the measuringfunctionality of its measuring device electronics and/or for validatingmeasured values produced by means of the measuring device—wherein themethod comprises steps as follows:

-   -   producing the working clock signal by means of the first clock        signal generator and clocking the processor with the working        clock signal;    -   producing the first reference clock signal by means of the first        clock signal generator;    -   producing the second reference clock signal by means of the        second clock signal generator;    -   producing, by means of the processor, the measured values        representing the at least one measured variable, for example,        based on the at least one measurement signal as well as based on        the working clock signal as the time base and/or frequency base        for the at least one measurement signal or the measured values;    -   ascertaining a frequency difference, which represents a        difference between the instantaneous clocking frequency of the        first reference clock signal and the instantaneous clocking        frequency of the second reference clock signal; and    -   generating an error report, which signals that at least one of        the two clock signal generators is delivering a reference clock        signal with an instantaneous clocking frequency, which deviates        by a predetermined degree from a nominal clocking frequency        respectively predetermined therefore, and/or which signals that        measured values ascertained by means of the processor are        erroneous or unreliable by more than a predetermined degree, if        the instantaneous clock frequencies of the first and second        reference clock signals deviate from one another by more than a        predetermined degree.

According to a first embodiment of the measuring device electronics ofthe invention, it is provided that, for producing the first referenceclock signal, the first clock signal generator has a frequency dividerfor the working clock signal.

According to a second embodiment of the measuring device electronics ofthe invention, it is provided that, for producing the working clocksignal, the first clock signal generator has a frequency multiplier forthe first reference clock signal, for example, one formed by means of aPLL circuit and/or by means of an FLL circuit.

According to a third embodiment of the measuring device electronics ofthe invention, it is provided that the clocking frequency of the firstreference clock signal is different from the clocking frequency of thesecond reference clock signal, for instance in such a manner that theclocking frequency of the first reference clock signal is lower than theclocking frequency of the second reference clock signal.

According to a fourth embodiment of the measuring device electronics ofthe invention, it is provided that the processor is equipped, based onthe first reference clock signal as well as based on the secondreference clock signal, to detect whether at least one of the two clocksignal generators is delivering a reference clock signal with aninstantaneous clocking frequency, which deviates by a predetermineddegree from the nominal clocking frequency respectively predeterminedtherefor. Developing this embodiment of the invention further, theprocessor is furthermore equipped to produce, making use of the tworeference clock signals, a report, for example in the form of an alarm,which signals that at least one of the two clock signal generators isdelivering a reference clock signal, which has an instantaneous clockingfrequency deviating from the nominal clocking frequency respectivelypredetermined therefor.

According to a fifth embodiment of the measuring device electronics ofthe invention, it is provided that the processor is equipped toascertain an instantaneous frequency difference, Δf, defined as adifference between the instantaneous frequency of the first referenceclock signal and the instantaneous frequency of the second referenceclock signal. Developing this embodiment of the invention further, theprocessor is equipped, furthermore, to compare the ascertainedinstantaneous frequency difference with a threshold valuepredeterminable therefor, which represents a maximum allowable frequencydifference. This occurs, for example also in such a manner that, if theascertained instantaneous frequency difference exceeds the thresholdvalue, the processor produces a report—for example, in the form of analarm—which signals that at least one of the two clock signal generatorsis delivering a reference clock signal, which has a clocking frequencydiffering from a nominal clocking frequency respectively predeterminedtherefor. For example, the processor can ascertain the instantaneousfrequency difference based on a signal frequency difference formed bymeans of the instantaneous clocking frequency of the first referenceclock signal and the instantaneous clocking frequency of the secondreference clock and/or based on a frequency quotient formed by means ofthe instantaneous clocking frequency of the first clock signal and theinstantaneous clocking frequency of the second clock signal.

According to a sixth embodiment of the measuring device electronics ofthe invention, it is provided that the two—for example, equallyconstructed—clock signal generators are held in the case of undisturbed,steady state operation at the same operating temperature.

According to a seventh embodiment of the measuring device electronics ofthe invention, it is provided that the first clock signal generator isplaced on a substrate—for example, a circuit board—which is, at least asregards its coefficient of thermal expansion, equal to a substrate—forexample, a circuit board—on which the second clock signal generator isplaced.

According to an eighth embodiment of the measuring device electronics ofthe invention, it is provided that the first clock signal generator andthe second clock signal generator are placed on one and the samesubstrate, for example, a circuit board.

According to a first further development of the measuring deviceelectronics, the measuring device electronics further comprises: Anon-volatile data memory for measuring and/or operating data generatedby means of the measuring device electronics.

According to a second further development of the measuring deviceelectronics, the measuring device electronics further comprises: Acounter controlled by one of the two reference clock signals and havinga count input for the other reference clock signal, namely the one notcontrolling the counter.

According to a first embodiment of the second further development of themeasuring device electronics, it is provided that the reference clocksignal present at the count input is that reference clock signal, whoseclocking frequency is higher than the clocking frequency of the otherreference clock signal, namely that controlling the counter.

According to a second embodiment of the second further development ofthe measuring device electronics, it is provided that the clockingfrequency of the reference clock signal controlling the counterdetermines a count interval, within which the counter counts clocksignals of the reference clock signal present at the count input, forexample, beginning at one.

According to a third embodiment of the second further development of themeasuring device electronics, it is provided that the processor isequipped, based on a count result for clock signals of the referenceclock signal present at the count input delivered by the counter, todetect whether at least one of the two clock signal generators isdelivering a reference clock signal with an instantaneous clockingfrequency, which deviates by a predetermined degree from the nominalclocking frequency respectively predetermined therefor.

According to a first embodiment of the measuring device of theinvention, it is provided that the processor of the measuring deviceelectronics is equipped to ascertain, making use of the working clocksignal as a reference—for example, as a time base—as well as making useof the at least one measurement signal, a measured value representingthe at least one measured variable.

According to a second embodiment of the measuring device of theinvention, it is provided that the measuring device is a measuringdevice measuring in a time-based and/or a frequency-based manner, forexample, a Coriolis mass flow measuring device, an ultrasonic flowmeasuring device, a vortex flow measuring device, an ultrasonic filllevel measuring device, or a microwave fill level measuring device.According to a first embodiment of the method of the invention, suchfurther comprises a step of storing the ascertained frequency differencein a non-volatile data memory of the measuring device electronics.Developing this embodiment of the method of the invention further, it isfurthermore provided that there is stored in the non-volatile datamemory a datum stating the point in time of the ascertaining of thefrequency difference—for example, a datum in the form of the day and thetime of day.

According to a second embodiment of the method of the invention, suchfurther comprises a step of storing the error report in a non-volatiledata memory of the measuring device electronics. Developing thisembodiment of the method of the invention further, it is furthermoreprovided that there is stored in the non-volatile data memory a datumstating the point in time of the generating of the error report—forexample, a datum in the form of the day and the time of day.

A basic idea of the invention is to test the measuring functionality ofmeasuring devices of the type being discussed by monitoring the clocksignal generator clocking the processor ultimately delivering themeasured values, as regards the ability of such clock signal generatorto function, by means of an additional clock signal generator, in that(reference) clock signals produced independently from one another bymeans of the two clock signal generators but nevertheless nominallyhaving a fixed frequency relationship are examined as to whether—and, ingiven cases, to what extent—their instantaneous frequency differencedeviates from the nominally predetermined frequency difference, andconsequently—to the extent present—a deviation of the instantaneousclocking frequency of the working clock signal from the clockingfrequency nominally predetermined therefor can be estimated veryreliably. Via such a recurringly performed comparison of theinstantaneous frequency difference with the nominal value predeterminedtherefore, a drift of the frequency difference too high for the desiredaccuracy of measurement, in the case of which frequency difference thusa disturbance of the constant operation of one of the two clock signalgenerators, and, in this respect, a corresponding inaccuracy of themeasured values determined based on the working clock signal generatedby the one clock signal generator is to be attended to, can very quicklybe detected and correspondingly be promptly signaled, or also traceablydocumented, for instance, by a corresponding annotation—in given casesmarked with date and time of day—in the “on-board”, non-volatile datamemory.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, as well as other advantageous embodiments thereof, willnow be explained in greater detail on the basis of the appended drawing,in the figures of which examples of embodiments are presented. Equalparts are provided in all figures with the equal reference characters;when such is required for reasons of perspicuity or when it otherwiseappears sensible, already mentioned reference characters are omitted insubsequent figures. Other advantageous embodiments or furtherdevelopments, especially also combinations of aspects of the inventioninitially explained only individually, will furthermore become evidentfrom the figures of the drawing, as well as also from the dependentclaims per se. The figures of the drawing show as follows:

FIG. 1 a and FIG. 1 b show a measuring device of industrial measurementsand automation technology—here embodied as a compact measuringdevice—for media flowing in pipelines, in different side views;

FIG. 2 shows schematically, in the manner of a block diagram, ameasuring device electronics, especially also one suitable for ameasuring device according to FIGS. 1 a, 1 b, with a measuringtransducer connected thereto;

FIG. 3 a and FIG. 3 b show in partially sectioned and perspective views,a measuring transducer of vibration type, especially one suited for ameasuring device according to FIGS. 1 a, 1 b, with a measuring tubevibrating during operation; and

FIG. 4 shows a circuit portion, especially also one suitable forimplementation in a measuring device electronics according to FIG. 2,respectively serving for verification of said measuring deviceelectronics, with two clock signal generators, a counter for (reference)clock signals generated by means of the two clock signal generators anda comparator for comparison of a count result delivered by the counterwith a reference value predetermined therefor.

DETAILED DESCRIPTION IN CONJUNCTION WITH THE DRAWINGS

FIG. 1 shows schematically an example of an embodiment of a measuringdevice especially suited for application in industrial measurements andautomation technology. The measuring device serves to measure at leastone physical and/or chemical, measured variable of a medium, such as,for instance, a powder, a low viscosity liquid, a high viscosity pasteand/or a gas, etc., conveyed in a medium transporting line, such as, forinstance, a pipeline or a flume, or containable in a container, such as,for instance, a tank or a flume, and can be implemented, for example, asshown here, as an in-line measuring device, namely a measuring deviceinsertable into the course of a pipeline (not shown). The measuredvariable can accordingly be, for example, a mass flow rate or a totaledmass flow of a medium flowing in a pipeline, a medium such as, forinstance, a liquid, a powder, a gas, etc., or can also be, for example,a fill level of a liquid in a tank. Alternatively or in supplementation,the measured variable can also be, for example, a density ρ and/or aviscosity η of a medium of the aforementioned type.

For registering the at least one measured variable, the measuring deviceincludes: a measuring transducer MT, which interacts with the medium tobe measured, and which is here insertable into the course of a pipeline(not shown) and through which the medium to be measured flows duringoperation, and which serves for transducing the at least one measuredvariable into at least one measurement signal dependent thereon; and,electrically coupled with measuring transducer MT, a measuring deviceelectronics ME for activating the measuring transducer and forevaluation of measurement signals delivered by the measuring transducer,thus, the at least one measurement signal dependent on the at least onemeasured variable. It is in such case especially provided that themeasuring device is implemented as a measuring device which measures ina time-based and/or a frequency-based manner, namely a measuring deviceascertaining measured values on the basis of a measured frequency, ameasured period, a measured phase angle and/or a measured timeseparation of selected reference values of the at least one measurementsignal; thus, for example, a Coriolis mass flow measuring device, anultrasonic flow measuring device, a vortex flow measuring device, anultrasonic fill level measuring device, a microwave fill level measuringdevice or a fill level limit switch with a vibrating immersion element.In corresponding manner, the measuring transducer can be, for example:An ultrasonic measuring transducer for registering an echo travel timeof ultrasonic waves correlated with a flow velocity of a fluid flowingin a line or correlated with a fill level of a fill substance held in acontainer, a vortex frequency transducer for registering a sheddingfrequency of Karman vortices correlated with a flow velocity of a fluidflowing in a line, a microwave module with an antenna or Goubau line forregistering an echo travel time of electromagnetic microwaves correlatedwith a fill level of a fill substance held in a container, or ameasuring transducer of vibration type with vibrating measuring tube forregistering a phase shift of local vibrations of the measuring tube, ascorrelated with a mass flow rate of a medium flowing through saidmeasuring tube and/or for registering a vibration frequency, which iscorrelated with a density of the medium located in the measuring tube.

FIG. 2 further shows schematically in the manner of a block diagram anexample of an embodiment of a measuring device of the type beingdiscussed—for example, one supplied with electrical energy duringoperation externally via connecting cable and/or by means of internalenergy storers—with a measuring device electronics, and a measuringtransducer connected thereto, this measuring transducer being hereembodied, by way of example, as a measuring transducer of vibration typewith at least one measuring tube, which is insertable into the course ofa pipeline, is flowed through during operation by medium to be measured,and is caused to vibrate. The measuring device electronics includes adriver circuit Exc serving for activating the measuring transducer—herenamely actively exciting vibrations of the measuring tube—as well as ameasuring and evaluating circuit μC processing the at least onemeasurement signal—embodied here as an oscillatory signal representingvibrations of the at least one measuring tube—of the measuringtransducer MT—namely a measuring and evaluating circuit μC formed bymeans of at least one processor clocked by a working clock signal clk0.During operation, measuring and evaluating circuit μC, making use ofworking clock signal clk0 as reference—for example as a time base orfrequency standard—and the at least one measurement signal, deliversmeasured values representing at least one measured variable, such as aninstantaneous mass flow rate or a mass flow totaled over a certain timeinterval. The at least one processor can be formed, as is quite usual inthe case of modern measuring devices or measuring device electronics ofthe type being discussed, for example, by means of a microprocessorand/or by means of a digital signal processor (DSP). Processors suitablefor such applications include, for example, those of the type SAM7CI ofthe firm, ATMEL Corp.

For producing the working clock signal clk0 clocking the processor, afirst clock signal generator CSG1 is furthermore provided in themeasuring device electronics. The clock signal generator CSG1 is, insuch case, equipped in such a manner that the working clock signal clk0generated therewith nominally has a constant clocking frequency f_(clk0)_(—) _(DES) (where DES stands herein for DESIRED). The clock signalgenerator CSG1 can be formed, for example, by means of a quartzoscillator and/or by means of a PLL circuit (phase locked loop) and/orby means of an FLL circuit (frequency locked loop), for example as anintegral component of the processor itself or also as a separateassembly implemented peripherally to the processor.

For additional explanation of the technical field of the presentinvention, FIGS. 3 a and 3 b show an example of an embodiment of ameasuring transducer of vibration type—for example, one suited forapplication in a Coriolis mass flow measuring device, a densitymeasuring device and/or a viscosity measuring device for flowing media.The measuring transducer MT—principally serving for registering measuredvariables of flowing media—is inserted during operation in the course ofa pipeline (not shown), through which flows the respective medium to bemeasured—for instance, a powdered, liquid, gaseous or vaporousmedium—and serves, as is known, to produce, in the flowing medium,mechanical reaction forces, especially Coriolis forces dependent on themass flow rate, inertial forces dependent on the density of the mediumand/or frictional forces dependent on the viscosity of the medium, whichreact measurably, especially in a manner registerable by sensor, on themeasuring transducer. Derived from these reaction forces describing themedium, by means of measuring and evaluating methods correspondinglyimplemented in the measuring device electronics, the mass flow rate mand consequently the mass flow, and/or the density ρ and/or a viscosityη of the medium, for example, can be measured in manner known to thoseskilled in the art.

For conveying flowing medium, such a measuring transducer of vibrationtype generally comprises at least one measuring tube 10—in the exampleof an embodiment shown in FIGS. 3 a and 3 b, a single, at leastsectionally curved measuring tube 10—accommodated in a measuringtransducer housing 100, wherein the measuring tube 10 extends with awanted oscillatory length between an inlet-side, first measuring tubeend 11# and an outlet-side, second measuring tube end 12#, and, forproducing the aforementioned reaction forces, is at least at timesduring operation actively excited to execute mechanical oscillations andcaused to vibrate across its wanted oscillatory length, and is in suchcase repeatedly elastically deformed, oscillating about a static restingposition. The wanted oscillatory length corresponds, in such case, to alength of an imaginary central, or also centroidal, axis (imaginaryconnecting line through the centers of gravity of all cross sectionalareas of the measuring tube) extending within the lumen; in the case ofa curved measuring tube, thus a stretched length of the measuring tube10. In its mechanical construction, as well as also its principle ofaction, the measuring transducer resembles the measuring transducersproposed in U.S. Pat. No. 7,360,451 or U.S. Pat. No. 6,666,098, or alsothose measuring transducers available from the assignee under the marks“PROMASS H”, “PROMASS P” or “PROMASS S”. Other measuring transducerscan, of course, also serve for implementing the invention; in the caseof measuring transducers of vibration type, thus also such with straightmeasuring tubes and/or more than one measuring tube, thus, for example,two or four measuring tubes, or also such comparable measuringtransducers as shown in the previously mentioned US-A 2010/0236338, US-A2010/0242624, US-A 2010/0242623, U.S. Pat. No. 6,006,609, U.S. Pat. No.6,513,393, U.S. Pat. No. 7,017,424, U.S. Pat. No. 6,840,109, U.S. Pat.No. 6,920,798, U.S. Pat. No. 5,796,011, U.S. Pat. No. 5,731,527 or U.S.Pat. No. 5,602,345, or, for example, also those measuring transducersavailable from the assignee under the marks “PROMASS I”, “PROMASS M”,respectively, “PROMASS E” or “PROMASS F”. In accordance therewith, themeasuring transducer embodied as a measuring transducer of vibrationtype can also have a single, straight measuring tube for conveyingmedium to be measured, or at least two measuring tubes which are, forexample, mechanically coupled with one another by means of an inlet-sideflow divider and an outlet-side flow divider, in given cases alsosupplementally by means of inlet and outlet-side coupling elements,and/or measuring tubes equally constructed to one another and/or curvedand/or parallel to one another, which, for producing the oscillationsignals, vibrate at least at times during operation, for instance, at anequal, shared oscillation frequency, but with opposite phase relative toone another.

For the typical case for such a measuring transducer of vibration type,wherein said measuring transducer MT is to be assembled releasably intothe process line (embodied, for example, as a metal pipeline), there areprovided, on the inlet side of the measuring transducer, a firstconnecting flange 13 for connection to a line segment of the processline supplying medium to the measuring transducer, and, on the outletside, a second connecting flange 14 for connection to a line segment ofthe process line removing medium from the measuring transducer. In suchcase, the connecting flanges 13, 14 can, as is quite usual in the caseof measuring transducers of the described type, also be integratedterminally into the measuring transducer housing 100.

In the case of measuring transducers of vibration type, the reactionforces required for registering the measured variable in the respectivemedium to be measured are, as is known, effected by causing the at leastone measuring tube to vibrate in an actively excited, oscillatory mode,the so-called wanted mode. Selected as the wanted mode is, in such case,as is quite usual in the case of measuring transducers of the type beingdiscussed, at least one of a large number of natural oscillation modesinherent to the at least one measuring tube, in which said measuringtube executes or can execute resonance oscillations about a restingposition and in each case having an oscillation node in the region ofits measuring tube ends and having at least one oscillatory antinode inthe region of its wanted oscillatory length, wherein the respectiveoscillation forms of these oscillations, as well as also theirrespective resonance frequency, is, as is known, decisively dependentalso on parameters of the medium flowing in the measuring tube,especially on its instantaneous density and viscosity. Particularly as aresult of this dependence on the medium flowing during operation throughthe at least one measuring tube and consequently through the measuringtransducer, the natural oscillation modes are variable during operationof the measuring transducer to a considerable degree. Depending on themanner of construction, application and measuring range, the resonancefrequencies can vary within a wanted frequency band ranging over some100 Hz or even in the kilohertz region. In the case of exciting the atleast one measuring tube to one of its instantaneous eigenfrequencies,or also resonance frequencies, an average density of the mediuminstantaneously flowing through the at least one measuring tube can, onthe one hand, thus easily be ascertained based on the instantaneouslyexcited oscillation frequency; on the other hand, the electrical powerinstantaneously required for maintaining the oscillations excited in thewanted mode can thus also be minimized.

For active excitation of vibrations of the at least one measuring tube,especially also those in the aforementioned wanted mode, the measuringtransducer shown here furthermore includes an exciter mechanism 40formed by means of at least one electro-mechanical—for example,electro-dynamic—oscillation exciter 41 in active connection with the atleast one measuring tube, wherein such exciter mechanism 40 serves tocause the at least one measuring tube operationally at least at times toexecute oscillations in the wanted mode in each case suitable for theparticular measuring—for example, bending oscillations in a naturalbending oscillation mode—with oscillation amplitudes in each casesufficiently large for producing and registering the above mentionedreaction forces in the medium, and, respectively, to maintain saidoscillations. The at least one oscillation exciter 41—which is, forinstance, electrodynamic and formed by means of plunging armature, orsolenoid, coils—and consequently the exciter mechanism 40, serves, insuch case, especially to convert an electrical excitation power P_(exc)fed from the measuring device electronics by means of at least oneelectrical driver signal s_(drv) into exciter forces F_(exc)—e.g.pulsating or harmonic, and thus essentially sinusoidal, exciter forcesF_(exc)—which correspondingly act on the at least one measuring tube,and thus bring about the desired oscillations in the wanted mode. Forexample, the at least one driver signal can simultaneously have aplurality of sinusoidal signal components with signal frequenciesdiffering from one another, of which a signal component—for instance,one at least at times dominating as regards signal power—has a signalfrequency corresponding to an instantaneous resonance frequency of anatural mode of oscillation selected as the wanted mode.

In such case, the exciter forces F_(exc)—generated by convertingelectrical excitation power P_(exc) fed into the exciter mechanism—can,in manner known to those skilled in the art, by means of the drivercircuit Exc provided in measuring device electronics ME—and hereultimately delivering the driver signal—correspondingly be tuned, forinstance, by means of electrical current controllers implemented in thedriver circuit and controlling an amplitude (electrical current level)of an electrical current of the driver signal and/or by means of voltagecontrollers controlling an amplitude (voltage level) of a voltage of thedriver signal, and, for example, by means of a phase control loop(PLL—phase locked loop) likewise provided in the operating circuit, asregards their instantaneous frequency, or in the case of amultifrequency excitation, as regards their instantaneous frequencies;compare for this, for example, also U.S. Pat. No. 4,801,897 or U.S. Pat.No. 6,311,136. The construction and application of the aforementionedphase control loop for active excitation of the measuring tubes tooscillations at one of their mechanical eigenfrequencies is described atlength, for example, in U.S. Pat. No. 4,801,897. Of course, also otherdriver circuits known by those skilled in the art to be suitable forsetting the exciter energy E_(exc) can be used, for example, also thoseaccording to the previously mentioned state of the art, for instance,the previously mentioned U.S. Pat. No. 4,777,833, U.S. Pat. No.4,801,897, U.S. Pat. No. 4,879,911, U.S. Pat. No. 5,009,109, U.S. Pat.No. 5,024,104, U.S. Pat. No. 5,050,439, U.S. Pat. No. 5,804,741, U.S.Pat. No. 5,869,770, U.S. Pat. No. 6,073,495 or U.S. Pat. No. 6,311,136.Furthermore, as regards an application of such driver circuits formeasuring transducers of vibration type, reference is made to themeasuring device electronics provided with measurement transmitters inthe series “PROMASS 83” as available, for example, from the assignee inconnection with such measuring transducers of vibration type, namelymeasuring transducers of the series “PROMASS E”, “PROMASS F”, “PROMASSH”, “PROMASS I”, “PROMASS P” or “PROMASS S”. Their driver circuit is,for example, in each case embodied in such a manner that bendingoscillations in the wanted mode are controlled at a constant amplitude,and thus one also largely independent of the density, ρ.

For registering vibrations of the at least one measuring tube 10,particularly also those actively excited by means of the at least oneoscillation exciter, the measuring transducer MT includes, furthermore,a corresponding sensor arrangement 50. This comprises, as is alsoschematically presented in FIGS. 3 a, 3 b, a first oscillation sensor51—for example, an electrodynamic, first oscillation sensor 51—arranged,here spaced apart from the at least one oscillation exciter, on the atleast one measuring tube 10, wherein this first oscillation sensor 51delivers a first oscillatory signal s_(sens1) representing vibrations ofthe measuring tube 10 and serving as a measurement signal of themeasuring transducer, for example, an electrical (alternating) voltagecorresponding to the oscillations, with an amplitude (voltage level)dependent on an instantaneous amplitude of the oscillations of the atleast one measuring tube. The oscillatory signal s_(sens1) can basicallycontain a plurality of signal components differing as regards theirsignal frequency, particularly also such, which correspond with theactively excited and, in this respect, desired oscillations of the atleast one measuring tube. Furthermore, the sensor arrangement can, as isusual in the case of such measuring transducers of vibration type—which,for instance, also serve for registering the mass flow rate—have asecond oscillation sensor 52, which is, for example, electrodynamic andconstructed equally to the first oscillation sensor 51, which isarranged spaced apart from the first oscillation sensor 51 on the atleast one measuring tube 10, and which delivers a second oscillatorysignal s_(sens2) likewise representing vibrations of measuring tube 10and serving as a further measurement signal of the measuring transducer.

The at least one oscillation sensor 51, and consequently the sensorarrangement 50 formed therewith, is, furthermore, as is usual in thecase of such measuring transducers, coupled in a suitable manner—forexample, wired via connecting lines—with a measuring and evaluatingcircuit correspondingly provided in the measuring device electronics,and here namely also formed by means of the at least one processor μC.The at least one measurement signal delivered by the measuringtransducer—here thus embodied as an oscillatory signal—is, as is alsoshown in FIG. 2, fed to the measuring device electronics ME, and thereto the measuring and evaluating circuit provided therein. Of course, theat least one oscillatory signal, or the oscillation signals s_(sense1),s_(sense2), are conditioned in a manner suitable for processing in theprocessor, and, consequently, the measuring and evaluating circuitformed therewith, and are especially converted by means of correspondingA/D converters into corresponding digital signals; compare for this, forexample, the previously mentioned U.S. Pat. No. 6,311,136 or U.S. Pat.No. 6,073,495, or also the aforementioned measurement transmitters ofthe series “PROMASS 83”. Accordingly, the at least one measurementsignal is first preprocessed, especially preamplified, filtered anddigitized, by means of a corresponding input circuit Cl of the measuringdevice electronics, namely one having an analog-to-digital converterA/D, in order thereafter to be capable of being suitably evaluated bymeans of the processor, and namely to be converted into the previouslymentioned, measured values representing, for example, a mass flow rate,a totaled mass flow and/or a density and/or a viscosity of the medium tobe measured; this occurs, in given cases, also taking into considerationelectrical excitation power fed by means of the at least one driversignal into the exciter mechanism, and consequently also convertedtherein. In such case, working clock signal clk0 can furthermore also beused, matched to the working clock speed of the processor, to clockinput circuit Cl or the A/D-transducer provided therein, or to serve asa basis for a corresponding working clock signal clk0′ for input circuitCl.

Used as input circuit Cl, as well as also as measuring and evaluatingcircuit μC can be established circuit technologies or control orevaluating programs such as, for instance, those already applied inconventional Coriolis mass flow measuring devices for the purpose ofconverting the oscillation signals or for ascertaining mass flow ratesand/or totaled mass flows, etc. The program code for such controlprograms serving for control of the measuring transducer and/orevaluating programs serving for generating measured values can, forexample, be lastingly stored in a non-volatile data memory EEPROM of themeasuring device electronics in given cases serving for storing measuredvalues generated by means of the measuring device over a longer periodof time, and, in the case of starting up the measuring deviceelectronics, be loaded into a volatile data memory RAM, e.g. oneintegrated in the processor. Equally, by means of measuring deviceelectronics ME, measured values generated during operation can be loadedto such a—in given cases, also the same—volatile data memory RAM, andcorrespondingly held for later further processing.

In the case of application in a Coriolis mass flow measuring device, themeasuring device electronics especially serves, making use of themeasurement signals generated by the measuring transducer in the case ofa measuring tube 10 oscillating partially in wanted and partially inCoriolis mode, namely based on a phase difference detected between theoscillation signals s_(sens1), s_(sesn2) of the first and secondoscillation sensors 51, 52, recurringly to ascertain as exactly aspossible a mass flow measured value X_(m), which represents the massflow rate, m, to be measured for the medium guided through the measuringtransducer. Alternatively thereto or in supplementation thereof, themeasuring and evaluating circuit, as is quite usual in the case ofmeasuring devices formed by means of a measuring transducer of vibrationtype, can, in given cases, also be used to ascertain a density measuredvalue X_(ρ) representing the density of the medium and/or a viscositymeasured value X_(η) representing a viscosity of the medium; compare forthis also the previously mentioned U.S. Pat. No. 7,284,449, U.S. Pat.No. 7,017,424, U.S. Pat. No. 6,910,366, U.S. Pat. No. 6,840,109, U.S.Pat. No. 5,576,500 or U.S. Pat. No. 6,651,513.

The measured values generated by means of the measuring and evaluatingcircuit can be displayed, for example, on-site. For on-site visualizingof measured values produced internally in the measuring device and/or ingiven cases system status reports generated internally in the measuringdevice, such as, for instance, an error report or an alarm, themeasuring device can have, for example, a display and servicing elementHMI which is in communication with the measuring device electronics andin given cases is also portable, such as, for instance, an LCD, OLED orTFT display placed in the electronics housing behind a windowcorrespondingly provided therein as well as a corresponding input keypadand/or a touch screen. Advantageously, the measuring deviceelectronics—which is, for example, also remotely parameterable—canfurthermore be designed in such a manner that, during operation of themeasuring device, it can exchange measuring and/or other operatingdata—such as, for instance, current measuring and/or system diagnosisvalues, or setting values serving for control of the measuringdevice—with a superordinated electronic data processing system—forexample, a programmable logic controller (PLC), a personal computerand/or a work station—via a data transmission system, for example, afieldbus system and/or wirelessly via radio. Furthermore, measuringdevice electronics ME can be designed in such a manner that it can befed by an external energy supply, for example, also via theaforementioned fieldbus system. For the case in which measuring device 1is equipped for connection to a fieldbus or other communication system,measuring device electronics ME—which is, for example, also (re-)programmable on-site and/or via a communication system—can additionallyhave a corresponding communication interface for data communication,e.g. for sending measuring and/or operating data, and consequently themeasured values representing at least one measured variable, to thealready mentioned programmable logic controller or to a superordinatedprocess control system, and/or for receiving settings data for themeasuring device. Particularly for the case, in which the measuringdevice is provided for coupling to a fieldbus or other communicationsystem, measuring device electronics ME consequently furthermoreincludes a communication interface COM for data communication, embodiedaccording to one of the relevant industry standards. Moreover, measuringdevice electronics ME can have, for example, such an internal energysupply circuit ESC, which, during operation, is fed via theaforementioned fieldbus system from an external energy supply providedin the aforementioned data processing system. In such case, themeasuring device electronics can furthermore be embodied in, forexample, such a manner that it is electrically connectable by means of atwo-wire connection 2 L—configured, for example, as a 4-20 mA currentloop—with the external electronic data processing system, and can besupplied thereby with electrical energy, as well as transmit measuredvalues to the data processing system; the measuring device can, however,for example, also be embodied as a so-called four-conductor measuringdevice, in the case of which the internal energy supply circuit ESC ofmeasuring device electronics ME is connected by means of a first pair oflines with an external energy supply and the internal communicationcircuit COM of the measuring device electronics ME is connected by meansof a second pair of lines with an external data processing circuit or anexternal data transmission system.

The measuring device electronics, and consequently the driver circuitExc and the measuring and evaluating circuit μC, as well as otherelectronics components of the measuring device electronics serving foroperation of the measuring device, such as, for instance, the mentionedinternal energy supply circuit ESC for providing internal supplyvoltages U_(N) and/or the mentioned communication circuit COM servingfor connection to a superordinated measurement data processing systemand/or a fieldbus are furthermore advantageously accommodated in acorresponding electronics housing 200, especially an electronics housing200 embodied in an impact-resistant and/or also explosion-resistantmanner, and/or one embodied in a hermetically sealed manner and/orconstructed modularly. The electronics housing can be arranged, forexample, removed from the measuring transducer, or, as shown in FIGS. 1a, 1 b, be affixed, forming a single compact device, directly onmeasuring transducer MT; for example, externally affixed on transducerhousing 100. In the case of the example of an embodiment shown here, anecklike transition piece serving for holding the electronics housing200 is consequently furthermore placed on the transducer housing 100.Within the transition piece, an accommodation for electrical connectinglines, for example, an accommodation manufactured by means of glassand/or plastic potting compound or a hermetically sealed and/orpressure-resistant accommodation, can furthermore be arranged betweenmeasuring transducer MT—here, for example, thus the oscillation excitersand sensors placed therein—and measuring device electronics ME.

As already previously mentioned, in the case of measuring deviceelectronics of the type being discussed, and consequently measuringdevices formed therewith—particularly, however, also those which measurein a time-based and/or a frequency-based manner—it is of immenseimportance, that the working clock signal clk0 clocking the processorand ultimately serving as a reference—namely as time base or frequencystandard—for the at least one measurement signal or the measured valuesderived therefrom always has during operation, and namely in the case ofall operating conditions specified for the measuring device, aninstantaneous clocking frequency, which exactly corresponds to thenominal clocking frequency f_(clk0) _(—) _(DES), and consequently isreliably constant over as broad an operating range as possible and aslong a duration of operation as possible. In other words, formaintaining the accuracy of measurement designated for the particularmeasuring device, it is essential that the clock signal generator to alarge degree always runs uniformly, and namely delivers a working clocksignal with a non-varying (or at most, negligibly varying) clockingfrequency.

For estimating a risk that the clock signal generator is no longersufficient for the stated requirements regarding its precision, andconsequently for verifying the measuring functionality of the measuringdevice electronics or for validating the measured values ultimatelyproduced by means of the measuring device also during operation of themeasuring device, it is consequently provided in the case of themeasuring device electronics of the invention, that, in addition toworking clock signal clk0, the clock signal generator CSG1 furthermorealso produces a first reference clock signal clk1 dependent thereon,having a nominally constant clocking frequency f_(clk1) _(—) _(DES),which is smaller than the clocking frequency, f_(clk0) _(—) _(DES), ofthe working clock signal by a predetermined ratio R_(clk1)(R_(clk1)=f_(clk0) _(—) _(DES)/f_(clk1) _(—) _(DES)), especially morethan two times smaller (R_(clk1)>2). Moreover, the measuring deviceelectronics includes a second clock signal generator CSG2, whichproduces a second reference clock signal clk2 independent of workingclock signal clk0—and here particularly serving as a reference forworking clock signal clk0—with a nominally constant clocking frequencyf_(clk2) _(—) _(DES), which is likewise smaller than the clockingfrequency, f_(clk0) _(—) _(DES), of the working clock signal by apredetermined ratio R_(clk2) (R_(clk2)=f_(clk0) _(—) _(DES)/f_(clk2)_(—) _(DES)), thus, for example, in turn, more than a two times(R_(clk2)>2) smaller. Clock signal generator CSG2 can—for instance,analogously to the clock signal generator CSG1—be formed, for example,by means of a quartz oscillator, by means of a PLL circuit and/or bymeans of an FLL circuit. According to an additional embodiment of theinvention, the two (for example, equally constructed) clock signalgenerators CSG1, CSG2 are in such case furthermore equipped in such amanner that the clocking frequency of the first reference clock signalclk1 differs from the clocking frequency of the second reference clocksignal clk2, so that for the clocking frequency of both reference clocksignals, f_(clk1) _(—) _(DES)< >f_(clk2) _(—) _(DES), and consequentlyR_(clk1)< >R_(clk2), is true. This occurs especially also in such amanner that the clocking frequency of the first reference clock signalclk1 is lower than the clocking frequency of the second reference clocksignal clk2, and consequently, f_(clk1) _(—) _(DES)<f_(clk2) _(—)_(DES), and, respectively, R_(clk1)>R_(clk2).

Based on the two reference clock signals clk1, clk2—which are certainlygenerated independently of one another, but as a result of theirrespective, nominally constant, clock frequencies f_(clk1) _(—) _(DES)and f_(clk2) _(—) _(DES), have nevertheless a nominally constant, andconsequently invariant frequency relationship (f_(clk1) _(—)_(DES)/f_(clk2) _(—) _(DES)=constant) relative to one another—and via asimple, and in given cases recurringly performed observation of saidfrequency relationship, for example, via a simple comparison of acharacterizing value derived from both instantaneous clock frequenciesf_(clk1) _(—) _(ACT), f_(clk2) _(—) _(ACT) (where ACT stands herein forACTUAL) and with a threshold value predetermined therefor, it can thusvery quickly be recognized whether at least one of the two clock signalgenerators CSG1, CSG2 delivers a reference clock signal with aninstantaneous clocking frequency f_(clk1) _(—) _(ACT), or f_(clk2) _(—)_(ACT), which deviates from the nominal clocking frequency respectivelypredetermined therefore, f_(clk1) _(—) _(DES), respectively f_(clk2)_(—DES) , by a predetermined degree Δf_(allowed) or beyond, and, as aresult of this, care is to be taken that measured values ascertained bymeans of the processor can be erroneous by more than a predetermineddegree Δerr_(allowed)˜Δf_(allowed) allowable or acceptable therefor, andconsequently may not be reliable. Accordingly, according to anadditional embodiment of the invention, the processor is equipped, basedon the first reference clock signal clk1 as well as based on the secondreference clock signal clk2, to detect whether at least one of the twoclock signal generators is delivering a reference clock signal with aninstantaneous clocking frequency, f_(clk1) _(—) _(ACT), or f_(clk2) _(—)_(ACT), which deviates from the respective nominal clocking frequencypredetermined therefor, f_(clk1) _(—) _(DES), or f_(clk2) _(—) _(DES),by a predetermined degree Δf_(allowed) or more. In such case, it isespecially furthermore provided, that the processor is able to ascertainan instantaneous frequency difference, Δf, defined as a differencebetween the instantaneous clocking frequency f_(clk1) _(—) _(ACT) of thefirst reference clock signal clk1 and the instantaneous clockingfrequency f_(clk2) _(—) _(ACT) of the second reference clock signalclk2. This particularly occurs also in order thereafter to compare theascertained instantaneous frequency difference, Δf, with a thresholdvalue predeterminable therefor, which represents a maximum allowablefrequency difference Δf_(allowed), or, based on this comparison, namelyif the instantaneous clock frequencies of the two reference clocksignals deviate from one another by more than a predetermined degree,and consequently the ascertained instantaneous frequency difference Δfexceeds the threshold value, to produce an error report, report err1 (oran accordingly coded error signal)—in given cases also declared as alarmand/or initiating another testing of the measuring device—which signalsthat at least one of the two clock signal generators CSG1, CSG2 deliversa reference clock signal, which has a clocking frequency differing froma nominal clocking frequency respectively predetermined therefor, andthat measured values ascertained by the processor are erroneous beyond apredetermined degree, respectively, unreliable, and consequently are tobe treated as invalid. The aforementioned comparison can, asschematically presented in FIG. 4, be performed in very simple manner,e.g. by means of a digital comparator C—for instance, one implemented inthe processor—which compares the ascertained frequency difference Δf ata comparison input COMP with the numerical value present at a referenceinput_(REF) at the run time of the processor, representing thepredetermined threshold value Δf_(allowed).

The instantaneous frequency difference Δf can be ascertained, forexample, by means of processor μC based on a frequency difference formedby means of the instantaneous clocking frequency f_(clk1) _(—) _(ACT) ofthe first reference clock signal clk1 and the instantaneous clockingfrequency f_(clk2) _(—) _(ACT) of the second reference clock signalclk2, for example in such a manner that Δf˜f_(clk1) _(—) _(ACT)−f_(clk2)_(—) _(ACT), and/or based on a frequency quotient formed by means of theinstantaneous clocking frequency of the first clock signal and theinstantaneous clocking frequency of the second clock signal, forexample, so that Δf˜f_(clk1) _(—) _(ACT)/f_(clk2) _(—) _(ACT).Alternatively or in supplementation, the processor can ascertain theinstantaneous frequency difference Δf, moreover, also based, forexample, on one or more of the relationships: Δf˜f_(clk2) _(—)_(ACT)−f_(clk1) _(—) _(ACT), Δf˜f_(clk2) _(—) _(ACT)/f_(clk1) _(—)_(ACT), Δf˜1−f_(clk2) _(—) _(ACT)/f_(clk1) _(—) _(ACT), Δf˜1−f_(clk1)_(—) _(ACT)/f_(clk2) _(—) _(ACT), and, moreover, based on practicallyany function, whose function values ultimately serving namely as ameasure for the frequency difference either become larger in the case ofa growing deviation of the two clock frequencies f_(clk1) _(—) _(ACT),f_(clk2) _(—) _(ACT) from one another, or, conversely, becomecorrespondingly smaller.

The respective ascertained frequency difference Δf or the error reporterr1 in given cases generated based on this can, for instance, for thepurpose of assuring a traceability of possible measuring device errorsor measured value errors required on the part of the operator of themeasuring point formed by means of the measuring device and/or on thepart of the authorities overseeing said measuring point and/or for thepurpose of a detailed documentation of the history of the measuringdevice, in each case be stored in the mentioned non-volatile data memoryEEPROM of the measuring device electronics, in given cases thus also ina corresponding historical data set of frequency differences Δfrecurringly recorded over a longer period of time, or error reports err1in given cases derived therefrom. In such case, a datum stating arespective point in time (thus date and time of day) of the ascertainingof the (recorded) frequency difference Δf or of the generating of the(recorded) error report, for example, can advantageously also in eachcase be supplementally suitably stored along with this in thenon-volatile data memory EEPROM.

As is, for example, also schematically presented in FIG. 4, serving forascertaining the instantaneous frequency difference Δf can be a counterZ, constructed, for instance, as a synchronous dual counter, with anenable input EN for one of the two reference clock signals, for examplethe first reference clock signal clk1, so that the counter Z is thuscontrolled by said reference clock signal, and with a count input forthe other reference clock signal, namely the reference clock signal notcontrolling the counter, for example the second reference clock signalclk2. In accordance therewith, the reference clock signal present at thecount input is preferably that reference clock signal, whose clockingfrequency is higher than the clocking frequency of the other referenceclock signal, namely the reference clock signal controlling the counter.Thus, the clocking frequency of the—low frequency or “slower”—referenceclock signal controlling the counter determines a count interval, withinwhich the counter clock signals of the—higher frequency, or“faster”—reference clock signal present at the count input counts,preferably in each case beginning at one. Accordingly, in the case ofthis embodiment of the invention, the processor is furthermore equipped,based on a count result z delivered by the counter Z for clock signalsof the reference clock signal present at the count input CLK, to detectwhether at least one of the two clock signal generators CSG1, CSG2delivers a reference clock signal with an instantaneous clockingfrequency, f_(clk1) _(—) _(ACT), or f_(clk2) _(—) _(ACT), which deviatesfrom the respective nominal clocking frequency predetermined therefor,f_(clk1) _(—) _(DES), or f_(clk2) _(—) _(DES), by the correspondinglypredetermined degree Δf_(allowed) (Δf_(allowed)˜Δerr_(allowed)). In FIG.4, the subscript ‘allowed’ is abbreviated as ‘ald’.

For the purpose of simplifying the setting of a clocking frequency ratiof_(clk1) _(—) _(DES)/f_(clk2) _(—) _(DES) in each case suited for theparticular type of application, such clocking frequency ratio f_(clk1)_(—) _(DES)/f_(clk2) _(—) _(DES) being defined as a ratio of the nominalclocking frequency of the first reference clock signal to the nominalclocking frequency of the second reference clock signal, andconsequently for producing reference clock signal clk1 with a nominalclocking frequency f_(clk1) _(—) _(DES) optimally matched to said typeof application, according to an additional embodiment of the invention,and as is also schematically presented in FIG. 4, clock signal generatorCSG1 is formed by means of a frequency divider—here namely having adivider ratio 1/R_(clk1) corresponding to the predetermined ratioR_(clk1)—for the working clock signal clk0. The clock signal generatorCSG1/frequency divider is operated by an oscillator, for example, aquartz oscillator, a PLL circuit and/or an FLL circuit. As analternative to the specified case, in which reference clock signal clk1is derived (by means of frequency dividing) from working clock signalclk0, working clock signal clk0 can, for example, also, on the otherhand, be derived from the first reference clock signal clk1, forinstance by the clock signal generator CSG1 having a frequencymultiplier—formed, for example, by means of a PLL circuit and/or bymeans of an FLL circuit—for the first reference clock signal clk1.Furthermore, as is also schematically presented in FIG. 4, for thepurpose of an as simple a setting of the clocking frequency ratiof_(clk1) _(—) _(DES)/f_(clk2) _(—) _(DES) as possible, the second clocksignal generator CSG2 can also be formed by means of a frequency dividerdriven by an oscillator—for example, a quartz oscillator—a PLL circuitand/or an FLL circuit, which, matched to the reference clock signaldelivered by the first clock signal generator as well as the clockingfrequency ratio f_(clk1) _(—DES) /f_(clk2) _(—) _(DES) ultimately to beset, has a divider ratio 1/R_(clk2) which is correspondingly reverselyproportional to the divider ratio R_(clk2).

In order to minimize or largely exclude possible disturbing influences(stemming from the measuring device electronics itself or individualcomponents thereof, particularly also possible disturbing influences asa result of temperature fluctuations over time within the measuringdevice electronics) on the two clock signal generators, and consequentlyon the working clock signal or reference clock signal respectivelygenerated therewith, according to an additional embodiment of theinvention, it is provided that the first clock signal generator isplaced on a substrate, for instance a circuit board, for which, at leastas regards its coefficient of thermal expansion, especially also asregards its specific heat capacity and/or thermal conductivity, is equalto a substrate, on which the second clock signal generator is placed.This can be achieved, for example, in a simple as well effective manner,for example, by placing the first clock signal generator and the secondclock signal generator together on one and the same substrate, forexample, on one and the same circuit board. Furthermore, it can be ofadvantage, particularly also for preventing increased or alsounallowably high frequency differences (Δf>Δf_(allowed)) as a result ofpossible temperature gradients within the measuring device electronics,to hold the two clock signal generators CSG1, CSG2, at least in theundisturbed, steady operational case, at the same operating temperature;thus for example, to arrange them along a shared isotherm which extendsin as locationally fixed a manner as possible or as invariant a manneras possible in the measuring device electronics. This can be achieved,for example, by arranging the two clock signal generators—which are, ingiven cases, also placed on one and the same substrate—within themeasuring device electronics at as small a distance as possible from oneanother, and, consequently, within the electronics housing.

With the present invention, measuring devices of the aforementioned typecan thus recurringly—especially also regularly and/or withoutinterruption of actual measurement operation—be tested as to whether theworking clock ultimately serving as a basis for the measured valuesgenerated by means of the processor signal reliably exhibits or hasexhibited a clocking frequency lying within the specified tolerancelimits, or whether the clock signal generator CSG1 delivering theworking clock signal after a certain point in time, for instance as aresult of aging and/or outer disturbing influences, is to be graded asno longer corresponding to specification, and consequently as no longerreliable. In other words, a deviation of an actual, instantaneousclocking frequency, f_(clk0) _(—) _(ACT), of the working clock signalfrom the desired clocking frequency nominally predetermined therefor,f_(clk0) _(—) _(DES), can thus very simply, as well very reliably beestimated during operation.

The invention claimed is:
 1. A measuring device electronics for ameasuring device, said measuring device electronics comprising: aprocessor; a first clock signal generator for producing a working clocksignal clocking the processor with a nominally constant clockingfrequency and for producing a first reference clock signal dependent onthe working clock signal, said first reference clock signal exhibiting anominally constant clocking frequency which is smaller than the clockingfrequency of the working clock signal by a predetermined factor; and asecond clock signal generator for producing a second reference clocksignal independent of the working clock signal, said second referenceclock signal exhibiting a nominally constant clocking frequency which issmaller than the clocking frequency of the working clock signal by apredetermined factor, wherein said processor is adapted to detect, basedon said first reference signal as well as based on said second referenceclock signal, whether at least one of said first and second clock signalgenerators is delivering a reference clock signal with an instantaneousclocking frequency, which deviates by a predetermined degree from thenominal clocking frequency respectively predetermined therefor.
 2. Themeasuring device electronics as claimed in claim 1, wherein: forproducing said first reference clock signal, said first clock signalgenerator includes a frequency divider for said working clock signal. 3.The measuring device electronics as claimed in claim 1, wherein: forproducing the working clock signal, said first clock signal generatorincludes a frequency multiplier for the first reference clock signal. 4.The measuring device electronics as claimed in claim 1, wherein: theclocking frequency of said first reference clock signal differs from theclocking frequency of said second reference clock signal.
 5. Themeasuring device electronics as claimed in claim 1, further comprising:a counter controlled by one of said two reference clock signals, saidcounter including a count input for the other reference clock signal,not controlling said counter.
 6. The measuring device electronics asclaimed in claim 5, wherein: said reference clock signal present at thecount input is that reference clock signal, whose clocking frequency ishigher than the clocking frequency of the other reference clock signal,namely that controlling the counter.
 7. The measuring device electronicsas claimed in claim 1, wherein: said processor is equipped, by makinguse of the two reference clock signals, to produce a report, whichsignals, that at least one of the two clock signal generators isdelivering a reference clock signal, which exhibits an instantaneousclocking frequency deviating from the nominal clocking frequencyrespectively predetermined therefor.
 8. The measuring device electronicsas claimed in claim 1, wherein: said processor is adapted to ascertainan instantaneous frequency difference defined as a difference betweenthe instantaneous clocking frequency of said first reference clocksignal and the instantaneous clocking frequency of said second referenceclock signal.
 9. The measuring device electronics as claimed in claim 8,wherein: said processor is adapted to compare the ascertainedinstantaneous frequency difference with a threshold valuepredeterminable therefor, which represents a maximum allowable frequencydifference.
 10. The measuring device electronics as claimed in claim 9,wherein: said processor is adapted to produce, if the ascertainedinstantaneous frequency difference exceeds the threshold value, a reportwhich signals that at least one of the two clock signal generators isdelivering a reference clock signal, which exhibits a clocking frequencydiffering from a nominal clocking frequency respectively predeterminedtherefor.
 11. The measuring device electronics as claimed in claim 8,wherein: said processor ascertains the instantaneous frequencydifference based on a frequency difference formed by means of theinstantaneous clocking frequency of said first reference clock signaland the instantaneous clocking frequency of said second reference clocksignal.
 12. The measuring device electronics as claimed in claim 8,wherein: said processor ascertains the instantaneous frequencydifference based on a frequency quotient formed by means of theinstantaneous clocking frequency of said first clock signal and theinstantaneous clocking frequency of said second clock signal.
 13. Themeasuring device electronics as claimed in claim 1, wherein: said twoclock signal generators are held in case of undisturbed, steady stateoperation at the same operating temperature.
 14. The measuring deviceelectronics as claimed in claim 1, wherein: said first clock signalgenerator is placed on a substrate which, at least as regards itscoefficient of thermal expansion, is equal to a substrate on which saidsecond clock signal generator is placed.
 15. The measuring deviceelectronics as claimed in claim 1, wherein: said first clock signalgenerator and said second clock signal generator are placed on one andthe same substrate.
 16. The measuring device electronics as claimed inclaim 1, further comprising: a non-volatile data memory for measuringand/or operating data generated by means of the measuring deviceelectronics.
 17. The measuring device electronics as claimed in claim 5,wherein said clocking frequency of the reference clock signalcontrolling the counter determines a count interval, within which thecounter counts clock signals of the reference clock signal present atthe count input.
 18. The measuring device electronics as claimed inclaim 1, wherein the processor is embodied as a digital signalprocessor.
 19. A method for testing a measuring device for measuring atleast one physical and/or chemical, measured variable of a mediumconveyed in a line or in a container, wherein the measuring deviceincludes a measuring device electronics and a measuring transducerelectrically coupled with said measuring device electronics fortransducing the at least one measured variable into at least onemeasurement signal dependent thereon, and wherein the measuring deviceelectronics includes: a processor, a first clock signal generator forproducing a working clock signal clocking the processor with a nominallyconstant clocking frequency and for producing a first reference clocksignal dependent on the working clock signal, said first reference clockexhibiting a nominally constant clocking frequency, which is smallerthan the clocking frequency of the working clock signal by apredetermined factor, and a second clock signal generator for producinga second reference clock signal independent of the working clock signal,said second reference clock exhibiting a nominally constant clockingfrequency, which is smaller than the clocking frequency of the workingclock signal by a predetermined factor, said method comprising:producing the working clock signal by means of the first clock signalgenerator and clocking the processor with said working clock signal;producing the first reference clock signal by means of the first clocksignal generator and producing the second reference clock signal bymeans of the second clock signal generator; producing, by means of theprocessor, measured values representing said at least one measuredvariable; ascertaining a frequency difference, which represents adifference between the instantaneous clocking frequency of the firstreference clock signal and the instantaneous clocking frequency of thesecond reference clock signal; and generating an error report, saiderror report signaling that at least one of the two clock signalgenerators is delivering a reference clock signal with an instantaneousclocking frequency, which deviates by a predetermined degree from anominal clocking frequency respectively predetermined therefor, and/orsaid error report signaling that measured values ascertained by means ofthe processor are erroneous or unreliable by more than a predetermineddegree, if the instantaneous clock frequencies of the first and secondreference clock signals deviate from one another by more than apredetermined degree.
 20. The method as claimed in claim 19, wherein:producing measured values representing said at least one measuredvariable includes using the at least one measurement signal as well asthe working clock signal as a time-basis and/or a frequency base. 21.The measuring device electronics as claimed in claim 1, wherein: theprocessor is embodied as a microprocessor.
 22. The measuring deviceelectronics as claimed in claim 1, wherein: the processor is embodied asa digital signal processor.
 23. The measuring device electronics asclaimed in claim 1, wherein: said first clock signal generator is formedby means of a quartz oscillator.
 24. The measuring device electronics asclaimed in claim 1, wherein: said first clock signal generator is formedby means of a PLL circuit.
 25. The measuring device electronics asclaimed in claim 1, wherein: said first clock signal generator is formedby means of a FLL circuit.
 26. The measuring device electronics asclaimed in claim 1, wherein: said second clock signal generator isformed by means of a quartz oscillator.
 27. The measuring deviceelectronics as claimed in claim 1, wherein: said second clock signalgenerator is formed by means of a PLL circuit.
 28. The measuring deviceelectronics as claimed in claim 1, wherein: said second clock signalgenerator is formed by means of a FLL circuit.
 29. The measuring deviceelectronics as claimed in claim 7, further comprising: a non-volatiledata memory adapted to store a datum containing a point in time ofgeneration of said report.
 30. The measuring device electronics asclaimed in claim 8, further comprising: a non-volatile data memoryadapted to store a point in time of ascertaining the frequencydifference.
 31. The measuring device electronics as claimed in claim 10,further comprising: a non-volatile data memory adapted to store a datumcontaining a point in time of generation of said report.
 32. A measuringdevice for measuring at least one physical and/or chemical, measuredvariable of a medium conveyed in a line, or in a container, saidmeasuring device comprising: a measuring device electronics and ameasuring transducer electrically coupled with said measuring deviceelectronics for transducing the at least one measured variable into atleast one measurement signal dependent thereon, wherein the measuringdevice electronics includes: a processor, a first clock signal generatorfor producing a working clock signal clocking the processor with anominally constant frequency and for producing a first reference clocksignal dependent on the working clock signal, said first reference clocksignal exhibiting a nominally constant clocking frequency which issmaller than the clocking frequency of the working clock signal by apredetermined factor, and a second clock signal generator for producinga second reference clock signal independent of the working clock signal,said second reference clock signal exhibiting a nominally constantclocking frequency which is smaller than the clocking frequency of theworking clock signal by a predetermined factor.
 33. The measuring deviceas claimed in claim 32, wherein: said processor of the measuring deviceelectronics is adapted, making use of the working clock signal asreference, as well as making use of the at least one measurement signal,to ascertain a measured value representing the at least one measuredvariable.
 34. The measuring device as claimed in claim 32, wherein: themeasuring device is a measuring device which measures in a time-basedand/or a frequency-based manner.
 35. The measuring device as claimed inclaim 32, wherein the measuring device is one of: a Coriolis mass flowmeasuring device, an ultrasonic flow measuring device, a vortex flowmeasuring device, an ultrasonic fill level measuring device, or amicrowave fill level measuring device.
 36. The method as claimed inclaim 19, further comprising: storing the error report in a non-volatiledata memory of the measuring device electronics.
 37. The method asclaimed in claim 19, further comprising: storing the ascertainedfrequency difference in a non-volatile data memory of the measuringdevice electronics.
 38. The method as claimed in claim 37, furthercomprising: storing, in the non-volatile data memory, a datum containinga point in time of generation of the error report and/or a point in timeof ascertaining the frequency difference.
 39. A measuring deviceelectronics for a measuring device, said measuring device electronicscomprising: a processor; a first clock signal generator adapted toproduce a working clock signal clocking the processor with a nominallyconstant clocking frequency and to produce a first reference clocksignal dependent on the working clock signal, said first reference clocksignal exhibiting a nominally constant clocking frequency, which issmaller than the clocking frequency of the working clock signal by apredetermined factor; a second clock signal generator adapted to producea second reference clock signal independent of the working clock signal,said second reference clock signal exhibiting a nominally constantclocking frequency, which is smaller than the clocking frequency of theworking clock signal by a predetermined factor; and a counter controlledby one of said two reference clock signals, said counter including acount input for the other reference clock signal, not controlling saidcounter; wherein: the clocking frequency of said reference clock signalcontrolling the counter determines a count interval, within which thecounter counts clock signals of the reference clock signal present atthe count input, and/or said reference clock signal present at the countinput is that reference clock signal, whose clocking frequency is higherthan the clocking frequency of the other reference clock signal, namelythat controlling the counter.
 40. The measuring device electronics asclaimed in claim 39, wherein: the processor is adapted to ascertain aninstantaneous frequency difference, defined as a difference between theinstantaneous clocking frequency of said first reference clock signaland the instantaneous clocking frequency of said second reference clocksignal.
 41. The measuring device electronics as claimed in claim 40,further comprising: a non-volatile data memory adapted to store a pointin time of ascertaining the frequency difference.
 42. The measuringdevice electronics as claimed in claim 39, wherein: the processor isadapted to detect, based on said first reference clock signal as well asbased on said second reference clock signal, whether at least one ofsaid first and second clock signal generators is delivering a referenceclock signal with an instantaneous clocking frequency, which deviates bya predetermined degree from the nominal clocking frequency respectivelypredetermined therefor.
 43. A measuring device electronics for ameasuring device, said measuring device electronics comprising: aprocessor; a first clock signal generator adapted to produce a workingclock signal clocking the processor with a nominally constant clockingfrequency and to produce a first reference clock signal dependent on theworking clock signal, said first reference clock signal exhibiting anominally constant clocking frequency, which is smaller than theclocking frequency of the working clock signal by a predeterminedfactor; a second clock signal generator adapted to produce a secondreference clock signal independent of the working clock signal, saidsecond reference clock signal exhibiting a nominally constant clockingfrequency, which is smaller than the clocking frequency of the workingclock signal by a predetermined factor; and a counter controlled by oneof said two reference clock signals, said counter including a countinput for the other reference clock signal, not controlling saidcounter; wherein: the processor is adapted to ascertain an instantaneousfrequency difference, defined as a difference between the instantaneousclocking frequency of said first reference clock signal and theinstantaneous clocking frequency of said second reference clock signal.44. The measuring device electronics as claimed in claim 43, wherein:the processor is adapted to detect, based on said first reference clocksignal as well as based on said second reference clock signal, whetherat least one of said first and second clock signal generators isdelivering a reference clock signal with an instantaneous clockingfrequency, which deviates by a predetermined degree from the nominalclocking frequency respectively predetermined therefor.
 45. Themeasuring device electronics as claimed in claim 43, further comprising:a non-volatile data memory adapted to storing the ascertained frequencydifference.